This invention relates to the field of door security systems. More specifically, this invention relates to the use of a push bar or exit bar for securing a doorway.
Push bars, also known as panic bars, which allow egress through a doorway while limiting ingress are well known components of door security and emergency systems. The conventional exit bar is mounted on the interior side of the door to be secured and is oriented generally horizontally across the interior face of the door. A manual push force on the bar toward the door face retracts a door latch bolt to permit opening of the door. Conventional exit bars typically employ a mechanical linkage to actuate the latch mechanism for unlatching the door. A handle can also be additionally provided on the exterior face of the door to allow ingress under certain circumstances. Exit bars have also been connected with alarm systems to warn security personnel of a door opening.
Conventional exit bar systems while enjoying great popularity have also exhibited a number of limitations. During periods of high traffic levels through a doorway, mechanical latch mechanisms of a conventional exit bar can experience a high rate of wear. To reduce wear on mechanical latch components, some conventional exit bars may be manually locked or xe2x80x9cdoggedxe2x80x9d, wherein the latches remain in a retracted state. However, each bar must be manually dogged and undogged at the site of the door, thus constant attention by building personnel is required. Further, manual dogging of door latches is not permitted on fire doors as the door must latch to prevent the spread of fire.
It is also known to employ exit bars in which the latch bolt can be retracted and dogged in a retracted state by an electrical signal. Electrical dogging of exit bar latches in a retracted state is allowed on fire doors. In some known exit bars of this type the electrical retraction system is interrelated with the mechanical retraction system. Thus, the electrical retraction system must be capable of actuating a mechanical retraction system. This requires an electrical retraction system having sufficient power to overcome the inertia associated with movement of the parts of the mechanical retraction system. Other known exit bars require complex motors and/or multiple electromagnetxe2x80x94armature assemblies and/or solenoids to achieve latch bolt retraction and dogging.
Briefly stated, the invention in a preferred form is an exit bar with dual, independent retraction systems. The exit bar is conventionally mounted to a face of a door. The door is pivotally mounted to one side of a door frame with the opposing side of the door frame fixedly mounting a strike. The exit bar includes a housing which is mounted to the door. A latch bolt extends from the end of the housing and cooperates with the strike for releasably latching the door to the frame. A manual latch retraction system includes a push pad defining an exposed push face for receiving a manual push force. A link system links the pad to the latch assembly for retracting the latch bolt when the pad is pushed. A separate electrical latch retraction system includes an electromagnet mounted within the housing and a power source for selectively supplying electrical power to the electromagnet. An armature has an attracted surface disposed oppositely a magnetic face of the electromagnet. The armature is pivotally mounted to an armature shroud at a position intermediate the ends of the armature. The shroud is pivotably mounted at one end to a shroud pivot. The shroud pivot is transversely displaceable within the housing and is biased away from the door face. The opposing end of the armature shroud is pivotally and slidingly engaged to the latch assembly. A biasing force biases one end of the armature away from the electromagnet, such that the attracted surface of the armature and the magnetic face of the electromagnet define a wedge shape gap. The electromagnet develops a strong magnetic field when supplied with electrical power. The strong magnetic field bridges at least a portion of the wedge shape gap imposing a magnetic force, which is greater than the armature biasing force, on the armature. Consequently, the armature is pulled toward and bonded with the electromagnet by the high magnetic force. Movement of the armature is transmitted through the armature shroud and electrical retraction system linkage to the latch assembly to thereby move the latch bolt to a retracted position withdrawn from the latch strike.
The manual and electrical retraction systems operate independently of one another. Thus, the push pad may be used to retract the latch bolt from the strike without actuating the electrical retraction linkage. Likewise, the electrical retraction system may be actuated without actuating the manual retraction linkage. Since the retraction systems are independent, the electromagnet is not required to overcome the inertia associated with moving parts of the manual retractor system. Thus an exit bar may incorporate a smaller electromagnet to retract the latch. Alternatively, the independent retraction systems allow a given electromagnet to successfully retract the latch against a greater pre-load exerted on a door, as compared to exit bars with interrelated retraction systems. Thus, the inventive exit bar has greater reserve strength than conventional systems to overcome adverse conditions, such as warped doors, wind load or other forces exerted on the door.
When electrical power is supplied to the electromagnet, the electrical retraction system will retract the latch bolt. Continued supply of electrical power to the electromagnet will maintain the latch bolt in the retracted position, holding the exit bar in a dogged state. Since the manual retraction system is independent of the electrical retraction system, the manual retraction system remains free to move in response to manually imposed forces. Ordinarily, this could lead to undesirable and unnecessary wear on components of the mechanical retraction system if they were continuously actuated while the exit bar is held in a dogged stated by the electrical retraction system. Accordingly, the mechanical retraction system preferably includes a dogging armature. When the exit bar is held in a dogged state by the electrical retraction system, the first manual displacement of the manual retraction system will engage and bond the dogging armature to the electromagnet, holding the mechanical retraction system in a dogged state wherein further movement and thereby wear is prevented.
An object of the invention is to provide a new and improved exit bar that may unlatch and dog in the unlatched position without requiring an outside mechanical force to retract the latch.
Another object of the invention is to provide an exit bar having an electromagnetic latch retractor which functions independently of a mechanical push pad.
A further object of the invention is to provide an exit bar in which a single electromagnet operates an electrical retraction system, dogs the electrical retraction system and dogs a mechanical retraction system.
Still another object of the invention is to provide an exit bar with manual and electric latch retractors, the exit bar further including a simple and effective mechanism for holding both retractors in a dogged state.